Copper alloys, e.g., bronze, may comprise a number of additional metals, including, but not limited to, tin, phosphorus, manganese, zinc, bismuth, iron, nickel and aluminum. By varying the percent composition of the metals, new alloys are achieved with different hardness, ductility, color, strength, etc. Copper alloys typically have a yellow-red color when newly cast, but may change to shades of green as a patina develops on the surface.
While it has been know for some time that the properties of copper alloys may be altered with addition of different elements, it has only recently been possible to produce copper alloys that are “white” or have a chromed-metal-like appearance and do not form a patina. One such white copper alloy is described in U.S. Pat. No. 6,149,739, issued Nov. 21, 2000, and incorporated herein by reference in its entirety. White copper alloys filled a long-felt need for metals which are easy to work and have low galling characteristics, but present a “clean” appearance (i.e., no patina). Such alloys were quickly adopted in sanitary settings, such as food handling, which required low galling and a clean appearance.
Recently, it has been discovered that elemental copper, and higher-copper content alloys have inherent antimicrobial properties. While the exact mechanism for this property is still the subject of intense research, one theory is that the copper surfaces interact with the outer membrane of bacteria to cause disruptive leakage of cytoplasm, and ultimately cell death. In view of these independent laboratory results, and following additional rigorous testing under U.S. Environmental Protection Agency (EPA)-approved protocols, the EPA certified 275 copper alloys (including brasses and bronzes) as public health antimicrobial products in 2008. Products made with these alloys, and approved for particular applications, such as hospital bed rails, may be marketed as “kills 99.9% of bacteria within two hours.”